1. Field of the Invention
This invention relates generally to Satellite Positioning Systems (“SPS”) devices, and in particular to a SPS device capable of providing fast update rates while being power conscious.
2. Related Art
The worldwide utilization of wireless devices such as two-way radios, pagers, portable televisions, personal communication system (“PCS”), personal digital assistants (“PDAs”) cellular telephones (also known a “mobile phones”), Bluetooth, satellite radio receivers and Satellite Positioning Systems (“SPS”) such as Global Positioning Systems (“GPS”), also known as NAVSTAR, is growing at a rapid pace. As the number of people employing wireless devices increases, the number of features offered by wireless service providers also increases, as does the integration of these wireless devices in other products.
However, wireless devices, in order to operate, receive power from portable power sources such as batteries. As these wireless devices increase in complexity by offering greater features and increased integration of different devices in a single product, the amount of power required to properly operate these wireless devices increases. As an example, there is a need for additional power as SPS devices are integrated into other wireless devices such as two-way radios, pagers, portable televisions, PCS, PDAs, cellular telephones, Bluetooth devices, satellite radio and other similar devices.
Unfortunately, energy is expensive and at times in short supply. Generally, portable power sources such as batteries have a limited battery time. Limited battery time results into limited continuous operation time of the wireless device. As an example, if a user (a user may be a person or an application) forgets to power off the wireless device the battery will drain and force the user to re-charge the battery before it can be utilized again.
However, for typical SPS applications, SPS devices do not have to operate continuously because a user may not need or desire to obtain the positional information of the SPS device (also known as a “fix” of the SPS device) continuously. This is generally true for applications involving a slow moving wireless device in an “open sky” (i.e., there are no obstructions to prevent the viewing of available satellites) environment. Examples of this situation may include traveling in an automobile on an open road, a marine vehicle (such as a ship or boat) in open waters, or hiking on an open path with a wireless device (such as a cellular telephone) with an integrated SPS receiver. A user may only need fixes at specific times (such as every 20 to 300 seconds) or on demand (such as when the user places an E911 call based on the new Federal Communication Commissions' “FCC” guidelines). As a result, operating the SPS receiver continuously in these situations would be a waste of limited power and result in shorter operation times for the wireless device. Therefore, there is a need in the art for a power management scheme capable of regulating the amount of power consumed by the SPS device based on the needs of wireless device and user.